Printing devices for printing on containers, e.g. bottles, are known in the prior art e.g. from WO 2009/018893. This publication describes a device for printing on containers by applying a print color or printing ink with print heads for a plurality of colors directly onto the outer surface of the container. This direct printing method competes against labelling and has various advantages in comparison with the labelling method, e.g. simplification of the filling plant or marketing reasons through the optical recognition of directly printed containers. In direct printing processes, containers are serially fed into a container treatment device, in which the containers are then directly printed. The treatment device consists of a rotor which is rotationally driven about a vertical machine axis, a printing unit and a device for drying the printing ink and/or causing it to set. The rotor comprises printing stations formed at regular angular intervals about the machine axis, the printing stations comprising a container support in the form of a rotary table that is rotatable about an axis parallel to the machine axis. Each printing unit may comprise e.g. four print heads for a CMYK color scheme for producing different color sets of a multicolor print as well as a further print head for areal printing or applying a transparent sealing or protective coating. In the WO 2009/018893 publication the print head is arranged on the rotor in opposed relationship with a rotary table and radially further inwards than the rotary table. The print head is additionally arranged such that it is displaceable relative to the rotary table in various axial directions, e.g. such that it moves along with the rotary table in accordance with the rotor movement, so that a container having a circular cross-section can be positioned in front of the print head such that each vertical nozzle row of e.g. an inkjet printer can be positioned at an arbitrary position of the curved container surface, e.g. the bottle surface, at a minimum distance therefrom so as to minimize the amount of color sprayed into the surroundings of the print head.
In particular when 3D bodies having curved or convex surfaces, e.g. bottles or the like, are printed on by means of drop-on-demand inkjet techniques, i.e. contactless, selective spraying-on of individual color droplets by means of a plurality of individual nozzles, it is particularly important that, during the printing process, external forces are, as far as possible, prevented from acting on the droplets exiting the printing nozzle. In addition to weight, electric fields, etc., the air current caused by the movement of the material to be printed on is an important factor. Uncontrolled air currents and turbulences etc. should be as small as possible and reduced to the smallest possible amount during the printing process. Furthermore, some droplets (undesired satellite droplets) are not placed on the substrate during the printing process, such satellite droplets polluting the area where the printing process takes place as a fine ink mist and impairing the print quality.
Due to the open structural design of the printing device according to WO 2009/018893 it is, however, impossible to prevent the inkjet from being deflected by non-foreseeable air currents, whereby the print will be rendered imprecise and parts of the system may also be contaminated with printing ink. Especially in the case of high bottle throughput rates, the resultant high conveying speeds will cause turbulences intensifying a formation of ink mists and leading to a deposit and accumulation of ink particles on machine components and the malfunctions resulting therefrom.
In order to avoid this, DE 10 2009 013477 A1 suggests, for the purpose of reducing contamination problems and improving the print quality, a printing device with a housing provided for printing bottles or similar containers in a rotationally driveable conveyor element with several printing positions. By means of the rotationally driveable conveyor element, the printing positions and/or the containers are moved on a self-contained path of movement between at least one container feed location and at least one container removal location. The print heads moving along with the printing positions and/or the containers are adapted to be moved relative to the outer surface of the respective container for applying a preferably multicolored print image to an outer surface area of the container to be printed on. In addition, a closed housing is suggested, said housing accommodating each container provided at a printing position during the printing process. A print head and a color-fixing device are stationarily integrated in the housing, i.e. such that they cannot be moved relative thereto. In addition, DE 10 2009 013477 A1 suggests means for extracting atomized and/or splashed consumables, such as printing ink.
A drawback of this device is, on the one hand, the complicated mechanism and control of the opening and closing elements of the housing on the rotating part. On the other hand, it is not possible to execute processes, which take place outside of the housing, on the object, e.g. a bottle, enclosed in the housing. In addition, this prior art only allows substantially cylindrical containers to be printed on, since the print head is located in the housing element.
One aspect of the present disclosure is the provision of a printing device for a container to be printed on in a rotationally-driven container conveying unit of a filling plant, the printing device preventing ink mists from depositing on components of the plant and from deteriorating the print quality. Another aspect of the present disclosure to provide a printing device for a filling plant, which is adapted to be used for arbitrary containers irrespectively of the size and the geometry of the containers and which is suitable for carrying out various processes, such as printing processes, marking processes, drying processes, pre-treatment and/or finishing treatment processes, conditioning processes etc.
A printing device of the type specified above includes a housing comprising a hollow body, which is partially open at least in a printing area and which is used for accommodating a container, the opening for the printing area defining a front side and a side located opposite the front side defining a rear side.
The partially open hollow body protects the printing area against draft, so that no ink mist can spread and thus damage components of the plant and deteriorate the print quality. In addition, the opening allows a flexible handling of processing tools, such as inkjet print heads, since the processing tools need not be integrated in the housing.
In particular, the housing may be configured such that various processing tools can releasably be attached to the opening of the partially open hollow body, the following processing tools being adapted to be used individually or in combination: single-color or multi-color inkjet print heads; an UV lamp; a surface conditioning device; a surface sealing device; and an extraction unit.
This will improve the flexibility of use of container printing tools. For example, processing tools used for printing can selectively be arranged stationarily with respect to the rotationally-driven container conveying unit or such that they are independent of the movement of the container conveying unit. Thus, arbitrary processing tools can be associated, at specific moments in time, with a specific printing position on the container to be printed on.
The component “partially open hollow body” of the partially open housing can be realized through various embodiments.
For example, the partially open hollow body normally comprises a cover and a side wall with at least one opening. According to one embodiment, the partially open side wall may be a circular cylinder cut-off in an axial direction, i.e. the partially open hollow body comprises a cover and a side wall with the opening, the side wall having a circular segment-shaped cross-section.
Normally, the printing devices used here are preferably devices with print heads making use of a demand-dependent inkjet, so-called “drop-on-demand” print heads. These devices/methods based on “drop/on/demand” may e.g. be inkjet print heads, piezo print heads, electrostatic print heads and/or printing valve printers.
According to another embodiment, the side wall may comprise two opposed flat lateral elements which are preferably configured as elements tapering conically, e.g. along a radial direction of the rotationally-driven container conveying unit. In the case of this embodiment, the available space is utilized in a particularly efficient manner.
According to a further development of the above, the partially open hollow body additionally comprises a rear-side element interconnecting the two flat elements at the rear of the open hollow body, thus producing a sealing effect against draft or ink mists.
According to one embodiment, the housing additionally comprises a mechanism for providing access to the space provided for the housing at a container feed location and at a container removal location of the rotationally-driven container conveying unit. This embodiment is advantageous in cases where the spatial conditions necessitate complicated robot arm movements for feeding and removing containers, so that complicated feed and removal mechanisms would be required. Feeding and removing processes can be simplified by a mechanism for providing access to the space provided for the housing.
The component “mechanism for providing access” to the partially open housing can be realized through various embodiments.
The mechanism for providing access to the space provided for the housing at a container feed location and at a container removal location of the rotationally-driven container conveying unit may also be realized through the embodiments following herein below.
According to one embodiment, the accessing mechanism is configured such that it moves the open hollow body away from the container reception position in a radial direction relative to an axis of rotation of the rotationally-driven container conveying unit, either in the direction of the axis of rotation of the rotationally-driven container conveying unit or outwards away from the axis of rotation of the container conveying unit.
According to another embodiment, the mechanism may be configured such that it moves the open hollow body upwards so as to open the space for accommodating the container.
According to a further embodiment, the accessing mechanism may be configured such that it folds the open hollow body rearwards about a horizontal axis, e.g. by means of a joint-like device.
According to an embodiment in which the side wall comprises two opposed flat lateral elements and a rear-side element, the partially open hollow body may be bipartite and the accessing mechanism may be provided with a joint on the rear side of the hollow body, so that the hollow body halves can be pivoted rearwards about a vertical axis. Alternatively, the side wall may have a circular segment-shaped cross-section. According to another variant, the mechanism is capable of moving the two hollow body halves apart in a horizontal direction tangentially to the direction of movement of the rotationally-driven container conveying unit.
According to another alternative embodiment, the partially open hollow body comprises a cover, two opposed flat lateral elements and a rear-side element interconnecting the flat elements on the rear side, the accessing mechanism being configured such that it is capable of displacing the flat lateral elements together, or preferably separately, to the rear. The preferred separate displacement offers, on the one hand, sufficient space for container feeding and removal and, on the other hand, a protective effect of the housing is preserved during such feeding and removal.
According to another embodiment, in which the partially open hollow body comprises a cover and a side wall having a circular segment-shaped cross-section, the side wall is bipartite along a vertical axis and the accessing mechanism is configured such that the side wall halves can be displaced rearwards about a common vertical axis of rotation for moving them one on top of the other.
According to a further embodiment, in which the open hollow body comprises flat lateral elements and a rear-side element, the flat lateral elements may be connected by a joint to the rear side, the accessing mechanism being configured such that the flat lateral elements can fold rearwards about a vertical axis through this joint. This embodiment allows two neighbouring housings to share a common partition and an accessing mechanism, which means that space and material are utilized in a particularly efficient manner.
Alternatively to the above-mentioned joint, the flat lateral elements may be configured such that they are resilient or flexible, so that they can be bent rearwards about a vertical axis. This simplifies the structural design, since neither and articulation mechanism nor an actuator are necessary for moving the lateral parts. Due to the flexibility of the flat lateral elements, the elements can be moved e.g. by the robot arms or gripping arms of the feeding and removing devices or by the object to be printed on itself.
According to a further embodiment, the printing device additionally comprises a plurality of tables having placed thereon at least one of the at least one housing, at least one container feeding device and at least one container removing device. The tables may be configured as rotary tables, so that e.g. a container which is to be printed on and which has a curved surface can be positioned more easily in front of respective nozzle rows of inkjet print heads. Preferably, a housing is provided for each table, which opens through the accessing mechanism the space provided for the housing at the container feeding device and the container removing device.
According to one embodiment, an extraction unit is provided in the side wall or on the table so as to extract ink mists that may perhaps occur and so as to provide, if necessary, constant flow conditions in the printing area.
Depending on the circumstances prevailing in the plant in question, the partially open hollow body can be arranged such that the opening of the housing and thus the front side of the housing is directed radially outwards or inwards with respect to the rotationally-driven container conveying unit. If the front side is directed radially outwards, the processing tools on the outer side of the rotationally-driven container conveying unit must be either fixedly associated with a container position or arranged such that they can flexibly be associated with a plurality of container positions. If the opening and thus the front side is directed radially inwards, the processing tools must be arranged in a corresponding manner on the inner side of the rotationally-driven container conveying unit. For feeding and removing containers, an additional opening, which an be closed, if necessary, may be provided on the rear side of the housing (on the side directed radially outwards according to the above definition of front and rear sides).
Making use of a rotary table, it is also possible to provide two openings in the housing, the respective openings being directed radially inwards and outwards with respect to the rotationally-driven container conveying unit. The printing position on the container may then be placed at the respective opening, e.g. by means of the rotary table.
According to one embodiment, the hollow body of the housing including an opening on at least one side thereof is connected to a container centering head above the table of the rotationally-driven container conveying unit, so that the container centering head can be used as a mechanism for lifting the housing thus providing access to the space provided for the housing at a container feed location and a container removal location.
Furthermore, a sealing means is provided between the side wall of the housing and the table according to one embodiment, said sealing means comprising e.g. brushes, a hydraulic seal, a bellows, a labyrinth seal or a combination thereof. Said sealing means efficiently improves a possibly executed extraction on the one hand and avoids uncontrolled air currents in the printing area on the other.
The present disclosure also relates to the housing as an independent unit, e.g. as a spare part in a filling plant.